The Hero Badge was removed from the game and is no longer attainable.
The Hero Badge was the hardest to earn out of the three first-stage badges (Bandit, Survivor and Hero). To obtain it, you had to kill three bandits, (players who killed innocent players) and survive for 3 days. Once you got an aggressive kill (a kill on a non-bandit), your Hero streak would be over, and you would have to start again. Obtaining the Hero Badge gave you a blue headband.